Formal Buddhist rituals generally do not incorporate music as such, with the exception of more recent denominations that have absorbed practices from Protestant Christianity. Chanting and rhythmic recitation use tones other than those of normal speech but are not usually done to musical accompaniment. Buddhist rituals do, however, make extensive use of a wide variety of sounds and percussive devices. Bells, gongs, drums, hollow blocks, and clappers of many sizes are standard equipment in different areas of temples and monasteries. Large and medium-sized bells signal the beginning of worship services, and Zen masters use smaller bells to signal the end of sessions with individual monks. Large drums announce the time for certain exercises and gatherings. The most common ritual use of sound devices is that of keeping time during recitation and chanting or scriptural texts. Hollow blocks make a hypnotic “klop” to focus the attention and heavy bronze bowls emit a rich lingering note that reminds worshippers of the impermanence of all things. The combination of sustained warm bell-like tones punctuated by stark wooden percussion is very effective and surprisingly easy to listen to. Buddhists in various parts of the world sometimes use music and dance para-liturgically—that is, outside of their primary ritual settings. Zen meditative mood, for example, is often associated with the haunting sound of the bamboo flute called the shakuhachi, and Tibetans have traditionally used vigorous dancing in ceremonies such as exorcism and other protective rituals.